Electrically heated element thermoelectric effect

ABSTRACT

Temperature estimation systems and methods for a powertrain of a vehicle, the powertrain comprising an electrically heated catalyst, utilize an electrical heater disposed proximate to the electrically heated catalyst, the electrical heater comprising a heating element and a controller configured to monitor a voltage of the electrical heater and estimate a temperature of the heating element of the electrical heater based on the monitored voltage of the electrical heater and a set of known thermoelectric effects. The estimated temperature could be utilized, for example, to estimate an exhaust gas temperature, which could then be leveraged for control of operating parameter(s) by the controller, such as engine fuel/air ratio.

FIELD

The present application generally relates to a vehicle electricallyheated catalyst (EHC) and, more particularly, to techniques forestimating exhaust system temperature(s) using the EHC andthermoelectric effect(s).

BACKGROUND

Exhaust gas resulting from combustion of an internal combustion engineis expelled from the cylinders and treated by an exhaust system tomitigate/eliminate emissions before release into the atmosphere. This istypically achieved by chemical reactions at one or more catalystsdisposed in the exhaust system. Exhaust gas temperature is a criticalcomponent for various aspects of engine control. This includes, but isnot limited to, engine emissions mitigation because these exhaust systemcatalysts(s) require a certain exhaust gas temperature range.Conventional techniques for measuring/estimating exhaust gas temperatureinclude using dedicated thermocouples and complex modeling techniques(e.g., resistance-based modeling). These conventional techniquesincrease engine costs and/or processing requirements. Accordingly, whilesuch conventional techniques do work well for their intended purpose,there exists an opportunity for improvement in the relevant art.

SUMMARY

According to one example aspect of the invention, a temperatureestimation system for a powertrain of a vehicle, the powertraincomprising an electrically heated catalyst, is presented. In oneexemplary implementation, the temperature estimation system comprises anelectrical heater disposed proximate to the electrically heatedcatalyst, the electrical heater comprising a heating element and acontroller configured to monitor a voltage of the electrical heater andestimate a temperature of the heating element of the electrical heaterbased on the monitored voltage of the electrical heater and a set ofknown thermoelectric effects.

In some implementations, the heating element of the electrical heatercomprises two dissimilar metals arranged in parallel between a powerterminal and a ground terminal. In some implementations, the controlleris configured to temporarily turn off a supply voltage to the electricalheater and monitor the voltage of the electrical heater as a voltagedifference between the power and ground terminals. In someimplementations, the controller is otherwise configured to turn on thesupply voltage to the electrical heater to thereby heat the electricallyheated catalyst. In some implementations, the set of knownthermoelectric effects includes the Seebeck effect.

In some implementations, the electrical heater is disposed upstream fromthe electrically heated catalyst. In some implementations, theelectrical heater is disposed mid-bed of or between one or morecatalysts of the electrically heated catalyst. In some implementations,the electrical heater is disposed downstream of the electrically heatedcatalyst. In some implementations, the powertrain does not include adedicated thermocouple for measuring a temperature relative to theelectrically heated catalyst. In some implementations, the controllerdoes not utilize a resistance-based temperature modeling technique tomodel a temperature relative to the electrically heated catalyst.

According to another example aspect of the invention, a temperatureestimation method for a powertrain of a vehicle, the powertraincomprising an electrically heated catalyst, is presented. In oneexemplary implementation, the temperature estimation method comprisesmonitoring, by a controller, a voltage of an electrical heater disposedproximate to the electrically heated catalyst, the electrical heatercomprising a heating element, and estimating, by the controller, atemperature of the heating element of the electrical heater based on themonitoring of the voltage of the electrical heater and a set of knownthermoelectric effects.

In some implementations, the heating element of the electrical heatercomprises two dissimilar metals arranged in parallel between a powerterminal and a ground terminal. In some implementations, the temperatureestimation method further comprises temporarily turning off, by thecontroller, a supply voltage to the electrical heater and monitoring thevoltage of the electrical heater as a voltage difference between thepower and ground terminals. In some implementations, the controller isotherwise configured to turn on the supply voltage to the electricalheater to thereby heat the electrically heated catalyst. In someimplementations, the set of known thermoelectric effects includes theSeebeck effect.

In some implementations, the electrical heater is disposed upstream fromthe electrically heated catalyst. In some implementations, theelectrical heater is disposed mid-bed of or between one or morecatalysts of the electrically heated catalyst. In some implementations,the electrical heater is disposed downstream of the electrically heatedcatalyst. In some implementations, the powertrain does not include adedicated thermocouple for measuring a temperature relative to theelectrically heated catalyst. In some implementations, the controllerdoes not utilize a resistance-based temperature modeling technique tomodel a temperature relative to the electrically heated catalyst.

Further areas of applicability of the teachings of the presentapplication will become apparent from the detailed description, claimsand the drawings provided hereinafter, wherein like reference numeralsrefer to like features throughout the several views of the drawings. Itshould be understood that the detailed description, including disclosedembodiments and drawings referenced therein, are merely exemplary innature intended for purposes of illustration only and are not intendedto limit the scope of the present disclosure, its application or uses.Thus, variations that do not depart from the gist of the presentapplication are intended to be within the scope of the presentapplication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a vehicle having a powertrain with anelectrically heated catalyst and an example temperature estimationsystem according to the principles of the present application;

FIG. 2 is a circuit diagram of the example temperature estimation systemof FIG. 1 according to the principles of the present application; and

FIG. 3 is a flow diagram of an example temperature estimation method fora vehicle having a powertrain with an electrically heated catalystaccording to the principles of the present application.

DESCRIPTION

As previously discussed, conventional techniques formeasuring/estimating exhaust gas temperature include using dedicatedthermocouples and complex modeling techniques (e.g., resistance-basedmodeling). These conventional techniques increase engine costs and/orprocessing requirements (e.g., large amounts of testing and calibrationfor complex modeling). Accordingly, improved exhaust gas temperatureestimation techniques are presented that leverage known thermoelectriceffect(s) (e.g., the Seebeck effect) to simply and accurately estimateexhaust gas temperature based on monitoring of the voltage of anelectrical heater in the exhaust system. Many engines already includeelectrically heated catalysts (EHCs) that comprise one or more catalystsand an electrical heater disposed upstream, mid-bed, or downstream ofthe catalyst(s). Based on the monitored voltage of the electrical heaterand the known thermoelectric effect(s), exhaust gas temperature can beestimated and then used for various engine controls (e.g., fuel/airratio adjustment for quick/accurate catalyst heating). These techniquescould potentially reduce engine/processing costs.

Referring now to FIG. 1 , a diagram of a vehicle 100 having a powertrain104 and an example temperature estimation system 150 (e.g., an exhaustgas temperature estimation system) according to the principles of thepresent application is presented. While the powertrain 104 is generallydescribed as an internal combustion engine (hereinafter, “engine 104”)herein, it will be appreciated that hybrid or electric powertrainconfigurations could be utilized. The engine 104 combusts a fuel/airmixture within cylinders (not shown) to generate drive torque that istransferred to a driveline 108 via a transmission 112 for vehiclepropulsion. Exhaust gas resulting from combustion is expelled into anexhaust system 116 that mitigates/eliminates emissions before releaseinto the atmosphere.

The exhaust system 116 includes an electrically heated catalyst (EHC)120 comprising one or more catalysts 124 and an electrical heater 128.The electrical heater 128 could be disposed mid-bed relative to thecatalyst 124, but it will also be appreciated that the electrical heater128 could be disposed between two or more catalysts 124 orupstream/downstream from the catalyst(s) 124. A controller 132 controlsoperation of the engine 104 including monitoring the electrical heater128 as part of the temperature estimation techniques of the presentapplication. This estimated temperature could then be utilized forvarious aspects of engine control, including, but not limited to,control by the controller 132 of a fuel/air ratio (FAR) of the engine104 for optimized emissions. It will be appreciated that in addition toexhaust gas temperature estimation based on the estimated temperature ofthe heating element, the estimated temperature of the heating element ofthe electrical heater 128 could be leveraged to estimate temperatures ofother components (e.g., other catalysts or components in the exhaustsystem 116).

Referring now to FIG. 2 , a circuit diagram 200 of the exampletemperature estimation system 150 according to the principles of thepresent application is illustrated. As shown, the temperature estimationsystem 150 generally comprises the electrical heater 128 and thecontroller 132. The electrical heater 128 comprises two dissimilar metalportions 204, 208 (Materials A and B) of a heating element arranged inparallel between a hot and cold junctions QH 212 and QL 216 associatedwith a heat source TH 220 and a heat sink TL 224, respectively.

As shown, electrical current flows in opposing directions through thetwo dissimilar metals and generates, via the known thermoelectriceffect(s) such as the Seebeck effect, a voltage across positive andnegative terminals 228 and 232. The exhaust gas temperature estimationtechnique of the present application also provides estimation accuracythat is less sensitive to edge cases (e.g., extremely cold temperatures)compared to other complex modeling techniques such as resistance-basedmodeling. In one exemplary implementation, the temperature estimationtechnique provides accurate exhaust gas temperature estimation whilealso still allowing the electrical heater to operate as intended (e.g.,to increase the exhaust gas temperature, such as during cold starts ofthe engine).

In addition to the Seebeck effect, the known Peltier and/or Thomsonthermoelectric effects could be taken into account as part of theexhaust gas temperature estimation technique of the present application.The term “thermoelectric effect” generally refers to the directconversion of temperature differences to electric voltage and vice-versavia a thermocouple. A thermoelectric device (e.g., the electrical heater128) creates a voltage when there is a different temperature on eachside.

Conversely, when a voltage is applied to it, heat is transferred fromone side to the other, creating a temperature difference. At the atomicscale, an applied temperature gradient causes charge carriers in thematerial to diffuse from the hot side to the cold side. This effect canbe used to generate electricity, measure temperature, or change thetemperature of objects. Because the direction of heating and cooling isaffected by the applied voltage, thermoelectric devices can be used astemperature controllers. The thermoelectric effect generally encompassesthese three separately identified effects: the Seebeck effect, thePeltier effect, and the Thomson effect. The Seebeck and Peltier effectsare different manifestations of the same physical process.

Referring now to FIG. 3 , a flow diagram of an example exhaust gastemperature estimation method 300 for a vehicle (e.g., vehicle 100)according to the principles of the present application is illustrated.At 304, the electrically heated catalyst 120 is provided comprising oneor more catalysts 124 and the electrical heater 128 disposed proximateto (e.g., upstream, mid-bed or between, or downstream of) the one ormore catalysts 124. At 308, the controller 132 monitors a voltage of theelectrical heater 128. At 312, the controller 132 estimates atemperature of the heating element of the electrical heater 128 based onthe monitoring of the voltage of the electrical heater 128 and a set ofknown thermoelectric effects.

This monitoring and temperature estimation could occur during a periodwhere the controller 132 temporarily turns off supply power to theelectrical heater 128 to thereby allow for this voltage monitoring.Otherwise, the controller 132 can turn on the supply voltage to theelectrical heater 128 to generate heat to thereby heat the electricallyheated catalyst 120. Lastly, at 316, the controller 132 optionallycontrols at least one operating parameter of the engine (e.g., FAR)based on the estimated exhaust gas temperature. The method 300 then endsor returns to 304 for one or more additional cycles.

It will be appreciated that the term “controller” as used herein refersto any suitable control device or set of multiple control devices thatis/are configured to perform at least a portion of the techniques of thepresent application. Non-limiting examples include anapplication-specific integrated circuit (ASIC), one or more processorsand a non-transitory memory having instructions stored thereon that,when executed by the one or more processors, cause the controller toperform a set of operations corresponding to at least a portion of thetechniques of the present application. The one or more processors couldbe either a single processor or two or more processors operating in aparallel or distributed architecture.

It should also be understood that the mixing and matching of features,elements, methodologies and/or functions between various examples may beexpressly contemplated herein so that one skilled in the art wouldappreciate from the present teachings that features, elements and/orfunctions of one example may be incorporated into another example asappropriate, unless described otherwise above.

1. A temperature estimation system for a powertrain of a vehicle, thepowertrain comprising an electrically heated catalyst, the temperatureestimation system comprising: an electrical heater of the electricallyheated catalyst disposed proximate to a catalyst of the electricallyheated catalyst, the electrical heater comprising a heating element; anda controller configured to: monitor a voltage of the electrical heater;estimate a temperature of the heating element of the electrical heaterbased on the monitored voltage of the electrical heater and a set ofknown thermoelectric effects; and estimate exhaust gas temperature of anengine of the powertrain based on the estimated temperature of theheating element, wherein the powertrain does not include a dedicatedthermocouple for measuring a temperature relative to the electricallyheated catalyst.
 2. The temperature estimation system of claim 1,wherein the heating element of the electrical heater comprises twodissimilar metals arranged in parallel between a power terminal and aground terminal.
 3. The temperature estimation system of claim 2,wherein the controller is configured to temporarily turn off a supplyvoltage to the electrical heater and monitor the voltage of theelectrical heater as a voltage difference between the power and groundterminals.
 4. The temperature estimation system of claim 3, wherein thecontroller is otherwise configured to turn on the supply voltage to theelectrical heater to thereby heat the catalyst of the electricallyheated catalyst.
 5. The temperature estimation system of claim 3,wherein the set of known thermoelectric effects includes the Seebeckeffect.
 6. The temperature estimation system of claim 1, wherein theelectrical heater is disposed upstream from the catalyst of theelectrically heated catalyst.
 7. The temperature estimation system ofclaim 1, wherein the catalyst of the electrically heated catalystcomprises one or more catalysts, and wherein the electrical heater isdisposed mid-bed of or between the one or more catalysts of theelectrically heated catalyst.
 8. The temperature estimation system ofclaim 1, wherein the electrical heater is disposed downstream of thecatalyst of the electrically heated catalyst.
 9. The temperatureestimation system of claim 1, wherein the controller does not utilize aresistance-based temperature modeling technique to model a temperaturerelative to the electrically heated catalyst.
 10. A temperatureestimation method for a powertrain of a vehicle, the powertraincomprising an electrically heated catalyst, the temperature estimationmethod comprising: monitoring, by a controller, a voltage of anelectrical heater of the electrically heated catalyst disposed proximateto a catalyst of the electrically heated catalyst, the electrical heatercomprising a heating element; estimating, by the controller, atemperature of the heating element of the electrical heater based on themonitoring of the voltage of the electrical heater and a set of knownthermoelectric effects; and estimating, by the controller, an exhaustgas temperature of an engine of the powertrain based on the estimatedtemperature of the heating element, wherein the powertrain does notinclude a dedicated thermocouple for measuring a temperature relative tothe electrically heated catalyst.
 11. The temperature estimation methodof claim 10, wherein the heating element of the electrical heatercomprises two dissimilar metals arranged in parallel between a powerterminal and a ground terminal.
 12. The temperature estimation method ofclaim 11, further comprising temporarily turning off, by the controller,a supply voltage to the electrical heater and monitoring the voltage ofthe electrical heater as a voltage difference between the power andground terminals.
 13. The temperature estimation method of claim 12,wherein the controller is otherwise configured to turn on the supplyvoltage to the electrical heater to thereby heat the catalyst of theelectrically heated catalyst.
 14. The temperature estimation method ofclaim 12, wherein the set of known thermoelectric effects includes theSeebeck effect.
 15. The temperature estimation method of claim 10,wherein the electrical heater is disposed upstream from the catalyst ofthe electrically heated catalyst.
 16. The temperature estimation methodof claim 10, wherein the catalyst of the electrically heated catalystcomprises one or more catalysts, and wherein the electrical heater isdisposed mid-bed of or between the one or more catalysts of theelectrically heated catalyst.
 17. The temperature estimation method ofclaim 10, wherein the electrical heater is disposed downstream of thecatalyst of the electrically heated catalyst.
 18. The method of claim10, wherein the controller does not utilize a resistance-basedtemperature modeling technique to model a temperature relative to theelectrically heated catalyst.